This invention relates to engine cylinder heads and more specifically is directed to a novel arrangement for thermally insulating an exhaust outlet in an engine cylinder head by providing a thermal insulator in a coolant passage adjacent the exhaust outlet.
In order to reduce the level of undesirable emission products in the exhaust of internal combustion engines and in improving the efficiency of the engine, it has been found desirable to limit the maximum temperature in the combustion chamber during combustion. However, it has now also been found desirable to keep the temperature of exhaust gases high once the gases leave the combustion chamber. Current engine cylinder head designs provide a coolant passage around the exhaust outlet passage from the combustion chamber and thus promote heat rejection from the exiting exhaust gases as soon as they leave the combustion chamber.
The present invention arises in part through the discovery that heat rejection by the exiting exhaust gases can be controlled and minimized immediately upon exiting the combustion chamber. The present invention accomplishes this by filling the coolant passage around the exhaust outlet passage in the cylinder head with a mixture of uncured epoxy resin and a curing agent, which is allowed to cure into a solid thermal insulator around the exhaust passageway either entirely or around selected portions thereof. The invention provides an uncomplicated and economical way of achieving the desired objective of minimizing heat rejection by the exiting exhaust gases before they are discharged through the exhaust system to the atmosphere.
The present invention is disclosed with reference to the ensuing description and claims and the accompanying drawings which describe and illustrate a preferred embodiment of the present invention according to the best mode presently contemplated in carrying out the invention.